Electronic part mounting device

ABSTRACT

The present invention is to provide an electronic part mounting device including: a lamination body composed of a circuit board and a structural member; an electronic part attached in an opening formed in the lamination body; and an encapsulant layer to encapsulate the electronic part, wherein an outer circumferential line of the opening is arranged inside an outer circumferential line of the encapsulant layer. Due to the foregoing arrangement, in the electronic part mounting device of the present invention, even if the device is bent, the encapsulant layer to encapsulate the electronic part is engaged with the circuit board or the structural member arranged inside the outer circumferential line of the encapsulant layer, so that electronic parts are prevented from coming off. Further, the manufacturing process is simple. Therefore, the cost of the electronic part mounting device can be greatly reduced.

TECHNICAL FIELD

The present invention relates to an electronic part mounting devicehaving an appropriate flexibility, the durability of which is high, andfurther the cost of which is low.

BACKGROUND ART

Concerning an electronic part mounting device represented by an IC card,it is conventionally required that the electronic part accommodated inthe device, such as a semiconductor chip and a wire coil, can besufficiently protected and the electronic part mounting device isappropriately flexible and durable.

(1) The Unexamined Japanese Patent Application Publication No. Hei.4-286697 discloses a personal IC card of high-performance characterizedin that: both the size and the flexibility of the IC card meet therequirements of ISO Standard; a semiconductor chip accommodated in theIC card can be sufficiently protected; the IC card is embossable; thedurability of the IC card is high; the cost of the IC card is low; andit is easy to manufacture the IC card. The IC card comprises: a circuitboard made of polyester film that has been heat-stabilized, the lengthand the width of which are the same as those of the final product of theIC card; a structural member having an opening, made to adhere onto anupper surface side of the circuit board with a thermoplastic adhesiveagent, the softening point of which is lower than that of the film, thelength and the width of which are the same as those of the circuitboard, the structural member being made of the same resin material asthat of the structural circuit board; electronic parts received in theopening and attached onto the circuit board; and an encapsulant layer,the rigidity of which is greater than that of the structural member,wherein the encapsulant is charged into the opening so as to seal theelectronic part.

(2) The Unexamined Japanese Patent Application Publication Nos. Sho.60-252992, Sho. 61-208188 and Hei. 3-166740 disclose an IC card made ofthermoplastic resin (polycarbonate resin), wherein the IC card isprevented from warping by a structure in which inner sheets of the samethickness, made of the same material, are symmetrically arranged on bothsides of a core sheet, and further cover sheets are also symmetricallyarranged on both sides of the core sheet, so that the thermal stress canbe well balanced.

(3) The Unexamined Japanese Patent Application Publication No. Sho.62-27195 discloses the following IC card for the purpose of providing asufficiently high mechanical strength and flexibility with respect tobending. In the IC card, an IC module is embedded in the base materialof the card, and the IC module includes a reinforcing member protrudingin the direction of an outer circumference of the IC module.

(4) In order to enhance the reliability of an IC card in the event thatbending stresses are given to the IC card, The Unexamined JapanesePatent Application Publication No. Hei. 2-235699 discloses an IC cardincluding a means for enhancing an adhering force between an encapsulantlayer to encapsulate an electronic part and a circuit board having aconductive pattern, and the means includes a plurality of holes formedclose to a mounting section of the electronic part on the circuit board,and a portion of the encapsulant which covers the electronic parts isinjected into the holes.

In the case of the IC card described in item (1), a sheet of polyesterresin film used on the IC card is made by means of drawing. Accordingly,it has a characteristic that the thinner the sheet of polyester resinfilm is, the lower the degree of thermal shrinkage and expansionbecomes.

Accordingly, even when sheets of polyester resin film are used whichhave been subjected to heat-stabilization before adhesion, when arelatively thick (about 350 μm thickness) sheet of film used for thestructural member is made to adhere onto a thin sheet of film used forthe circuit board, the joined body warps in the process of manufacturingan IC card. Therefore, it is difficult to manufacture the IC card.

The IC card described in item (2) is less susceptible to warp. However,when the IC card is bent, although it is an extreme condition, there isa possibility that an electronic part comes out from the opening of thestructural member together with the encapsulant layer. Therefore, theuse of the IC card described in item (2) is severely restricted.

According to the IC card described in item (3), the IC module containingan electronic part is prevented from coming out from the IC card.However, the structure becomes very complicated, and the manufacturingcost is raised.

According to the IC card described in item (4), the encapsulant layer toencapsulate the electronic part is made to strongly adhere onto thecircuit board. However, in the actual manufacturing process of this ICcard, it is necessary to use a very expensive molding machine referredto as a transfer molding machine by which the encapsulant layer isformed.

The present invention has been accomplished to solve the above problemsof the prior art. It is an object of the present invention to provide aninexpensive electronic part mounting device having an appropriateflexibility and high durability, and the performance of the electronicpart mounting device satisfies the requirements that the conventional ICcards meet.

DISCLOSURE OF THE INVENTION

The first invention is to provide an electronic part mounting devicecomprising: a lamination body composed of a circuit board and astructural member; an electronic part attached in an opening formed inthe lamination body; and an encapsulant layer to encapsulate theelectronic part, wherein an outer circumferential line of the opening isarranged inside an outer circumferential line of the encapsulant layer.

The second invention is to provide an electronic part mounting deviceaccording to the first invention, wherein the opening is composed of astructural member laminated on the circuit board.

The third invention is to provide an electronic part mounting deviceaccording to the second invention, wherein the structural memberincludes: a first structural member having a first opening, arranged onan upper surface side of the circuit board; and a second structuralmember having a second opening communicated with the first opening,arranged on an upper surface side of the first structural member, and anouter circumferential line of the first opening is arranged outside ofan outer circumferential line of the second opening.

The fourth invention is to provide an electronic part mounting deviceaccording to the third invention, wherein the circuit board is made ofthermoplastic resin, the length and width of which are substantially thesame as those of the final product, the first structural member ismainly made of thermoplastic resin, the length and width of which aresubstantially the same as those of the circuit board, the firststructural member is made to adhere onto an upper surface side of thecircuit board with a thermoplastic adhesive agent which is softened at atemperature lower than the softening point of the thermoplastic resin ofthe circuit board, the second structural member is made to adhere ontoan upper surface side of the first structural member with thesubstantially same adhesive agent as the above thermoplastic adhesiveagent, the length and the width of the second structural member aresubstantially the same as those of the circuit board, and theencapsulant layer is more rigid than the circuit board and the firststructural member.

The fifth invention is to provide an electronic part mounting deviceaccording to the fourth invention, wherein the thickness of the secondstructural member is substantially the same as the thickness of thecircuit board, and the second structural member is made of substantiallythe same resin as the resin of the circuit board.

The sixth invention is to provide an electronic part mounting deviceaccording to the fifth invention, wherein the thermoplastic resin is asheet of polyester film subjected to biaxial orientation andheat-stabilization, and the first structural member is made of thesubstantially same resin as the resin of the circuit board.

The seventh invention is to provide an electronic part mounting deviceaccording to claims 1 to 6, wherein the electronic part mounting deviceis an IC card.

It is possible to provide an encapsulant layer when a predeterminedresin is injected into and cured in an opening portion whichcommunicates the above structural members. However, when an electronicpart such as a semiconductor chip, which are frangible to an impact, areencapsulated, a rigid resin, the rigidity of which is higher than therigidity of the above structural members, is preferably used toencapsulate the electronic part, so that the semiconductor chip can beprotected from an impact given when the electronic part mounting deviceis bent. On the other hand, when an electronic part such as a wire coil,which is flexible, is encapsulated, it is not necessary to use a resinhaving the characteristic described above.

When the electronic part mounting device of the invention is an IC card,it is common that predetermined label sheets are attached onto the frontand the back side of the electronic part mounting device when theelectronic part mounting device is made to be a final product. In thiscase, the material and thickness of the label sheets on the front sideare preferably the same as those of the label sheet on the back side soas to make the thermal expansion property of the front label sheet to bethe same as that of the back label sheet. In this way, the IC card canbe prevented from warping. In this connection, it is preferable that thelabel sheet is made of thermoplastic resin such as polyvinyl chloridereferred to as PVC.

The reason why the circuit board and the structural plate arespecifically made from a sheet of polyester is described as follows. Theprice of polyester resin is lower than that of polyimide, and furtherpolyester resin is soft and embossable, and furthermore polyester resinis not easily softened by the heat given in the process of mounting theelectronic part. In this connection, polyester film includes a polyestermaterial to which a quantity of predetermined plasticizer and stabilizedare added.

In this connection, the above biaxial orientation is defined as follows.For example, polyester resin material extruded from an extruder is drawnin the longitudinal direction so that the molecular axis (fiber axis) ofpolyester is oriented in the longitudinal direction, and then it isdrawn in the lateral direction.

This sheet of polyester film, which has been subjected to biaxialorientation, is made in such a manner that heat-stabilization treatmentis conducted on the sheet of polyester film, in which the filmtemperature is raised to 150° C. at predetermined intervals. An amountof shrinkage of the sheet of film in an unrestricted condition that thetemperature is maintained at 150° C. for 30 minutes is smaller than 0.2%in both the longitudinal and the lateral direction, and a differencebetween the amount of shrinkage in the longitudinal direction and theamount of shrinkage in the lateral direction is smaller than 0.1%. Whenthe above sheet of film is used, it is possible to reduce a differencebetween the amount of shrinkage of the sheet of film composing thecircuit board and the amount of shrinkage of the sheet of film composingthe structural member, to be smaller than 0.1%.

From the viewpoints of reducing the material cost and enhancing theperformance, it is preferable that the thickness of each sheet of filmis not more than 250 μm, and it is more preferable that the thickness ofeach sheet of film is about 125 μm. The second structural member and thecircuit board are preferably made of the material of the samemanufacturing lot.

It is preferable that the adhesive agent used for the present inventionis a thermoplastic adhesive agent, because the thermoplastic adhesiveagent can appropriately absorb a strain caused between the members to beadhered so that the members can be prevented from warping. Especiallywhen sheets of polyester resin are made to adhere to each other, it ispreferable to use an adhesive agent made of ester.

According to the first invention, the electronic part mounting deviceincludes: an electronic part attached onto a circuit board and receivedin an opening; and an encapsulant layer by which the electronic part isencapsulated in the opening, wherein an outer circumferential line ofthe opening is arranged inside of an outer circumferential line of theencapsulant layer. Accordingly, even when the electronic part mountingdevice is bent, the encapsulant layer to encapsulate the electronic partcan be engaged with the structural member located inside of the outercircumferential line of the opening. Further, it is not necessary to usean expensive apparatus for forming the encapsulant layer.

According to the second invention, in addition to the action provided bythe first invention, the following action can be provided by a stepformed between the first opening and the second one. Even when theelectronic part mounting device is more intensely bent and theencapsulant layer to encapsulate the electronic part is separated fromthe second opening, the separating portion is located only at a positionclose to the surface of the second opening, that is, the separatingportion does not reach the first opening.

According to the third invention, the circuit board, the firststructural member and the second structural member are composed to besubstantially the same in length and width. Accordingly, in addition tothe action provided by the second invention, this electronic partmounting device can be manufactured easily in such a manner that thefirst structural member and the second one are laminated on an uppersurface of the circuit board, and the electronic part is mounted andthen encapsulated with an encapsulant, and a surface layer is arrangedon it if necessary. Further, the cost of the electronic part mountingdevice of the present invention is much lower than that of theconventional complicated electronic part mounting device of the priorart in which an IC module and other members must be further provided.

According to the fourth invention, the thickness of the secondstructural member is the same as the thickness of the circuit board, andthe second structural member and the circuit board are made of the samethermoplastic resin. Further, the second structural member and thecircuit board are substantially the same in length and width. In otherwords, the first structural member is interposed between the secondstructural member and the circuit board, that is, the second structuralmember and the circuit board are symmetrically arranged with respect tothe first structural member in the upward and downward direction.Accordingly, in addition to the action provided by the third inventiondescribed above, even when a change in temperature is caused between thecircuit board and each structural member in the process of mounting theelectronic part so that the thermal expansion and shrinkage occur, thefirst structural member is stably held by the circuit board and thesecond structural member. Therefore, the entire electronic part mountingdevice is not warped, and each member composing the electronic partmounting device expands and shrinks in the substantially same condition.

According to the fifth invention, all of the circuit board, the firststructural member and the second structural member are made from sheetsof polyester film which have been subjected to biaxial orientation andheat-stabilization. Accordingly, in addition to the action provided bythe fourth invention, it is possible to positively use an inexpensivethin sheet of polyester film, the heat expansion property of which isexcellent.

According to the sixth invention, the electronic part mounting device isspecified to an IC card. Actions provided by the first, second, third,fourth and fifth invention are very remarkably requested to the IC cardin which the electronic part mounting device of the invention is used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1!

A perspective view of the developed arrangement of Embodiment 1;

FIG. 2!

An enlarged view of the primary portion of FIG. 1;

FIG. 3!

A longitudinally cross-sectional enlarged view of the primary portion ofEmbodiment 1;

FIG. 4!

A longitudinally cross-sectional enlarged view of the primary portion ofEmbodiment 2;

FIG. 5!

A longitudinally cross-sectional enlarged view of the primary portion ofa variation of Embodiment 2;

FIG. 6!

A longitudinally cross-sectional enlarged view of the primary portion ofa variation of Embodiment 1.

Reference Characters, and Names!

1 . . . Circuit board

12 . . . Layer of adhesive agent on an upper side of the circuit board

14 . . . Conductive pattern

2 . . . Structural member

21 . . . First structural member

212 . . . Upper side adhesive agent layer of the first structural member

213 . . . Lower side adhesive agent layer of the first structural member

215 . . . First opening

22 . . . Second structural member

223 . . . Lower side adhesive agent layer of the second structuralmember

225 . . . Second opening

23 . . . Auxiliary structural member

233 . . . Lower side adhesive agent layer of the auxiliary structuralmember

235 . . . Opening of the auxiliary structural member

24 . . . Auxiliary circuit board member

242 . . . Upper side adhesive agent layer on the auxiliary circuit boardmember

245 . . . Opening of the auxiliary circuit board member

3 . . . Encapsulant layer

4 . . . Cover sheet

51 . . . Upper side label sheet

513 . . . Lower side adhesive agent layer on the upper side label sheet

52 . . . Lower side label sheet

522 . . . Upper side adhesive agent layer on the lower side label sheet

6 . . . Electronic part

BEST MODE FOR CARRYING OUT THE INVENTION EMBODIMENT 1

As shown in FIGS. 1 to 3, an IC card of the embodiment includes: acircuit board 1; a structural member 2 composed of a first structuralmember 21 attached onto an upper side of the circuit board 1, and asecond structural member 22; an encapsulant layer 3; a cover sheet 4arranged on an upper side of the encapsulant layer 3; and label sheets51, 52 composing both surface layers.

The above circuit board 1 is made of polyester resin, which is availableon the market, and the brand name of which is "Lumirror". The circuitboard 1 is formed from a substantially rectangular sheet of film, thesize of which is 85 mm×53 mm×125 μm. In this connection, on an uppersurface side of this circuit board 1, there is provided a predeterminedconductive pattern 14 which is formed as follows. A sheet of copper foilis made to adhere onto the upper surface side of this circuit board 1with a thermoplastic adhesive agent of ester (the brand name is "A412"manufactured by Sheldahl Inc.). In this case, the softening point of thethermoplastic adhesive agent is lower than that of the circuit board,and a quantity of the thermoplastic adhesive agent is determined so thatan adhesive agent layer 12 of 20 μm thickness can be formed in the finalproduct. After the sheet of copper foil has been made to adhere onto theupper surface side of the circuit board 1 in the above manner, etchingis conducted so as to form the conductive pattern 14. In order toenhance the anticorrosion property, this conductive pattern 14 issubjected to gold plating. On the circuit board 1, there are providedother electronic parts 6 such as an IC and a condenser used fortransmitting data.

The structural member 2 is composed of the first structural member 21arranged on the lower side and the second structural member 22 arrangedon the upper side.

The second structural member 22 is made of the same resin as that of thecircuit board 1. The size of the sheet of film from which the secondstructural member 22 is formed is the same as the size of the circuitboard 1 (85 mm×53 mm×125 (μm). Especially, the thickness of the secondstructural member 22 is the same as the thickness of the circuit board1.

As shown in FIGS. 1 to 3, in order to accommodate the electronic parts 6to be mounted on the circuit board 1, there are provided two openingportions 215, 225 which are formed from the upper surface side on eachof the structural members 21, 22 to the lower surface side. When bothstructural members 21, 22 are put upon each other, the opening portionsare communicated with each other, so that a communication hole can beformed, and a substantially flange-shaped step portion is formed in theboundary of both openings.

In this case, as shown in FIG. 1, outer circumferential lines of theopening portions 215, 225 are approximately square. However, the opening215 (the length of one side: 10 mm, the total length: 40 mm) arranged onthe lower side is larger than the opening 225 (the length of one side: 8mm, the total length: 32 mm) arranged on the upper side. Accordingly,when the communication hole is observed from the upper side, the outercircumferential line of the latter opening 225 is accommodated insidethe outer circumferential line of the former opening 215. The shape ofthe outer circumferential line of each opening portion may bearbitrarily determined. The shapes of both outer circumferential linesare not necessarily the same or the similar figures. Further, both outercircumferential lines may cross each other at several points, and one ofthe outer circumferential lines may be arranged inside the other outercircumferential line, and at the same time some of the outercircumferential lines may be arranged outside the other outercircumferential line.

In this connection, in this embodiment, other opening portions whichform other communicating holes not shown in FIGS. 2 and 3 are formedinto the same shapes as those of the above opening portions 215, 225,and also the positional relation of those opening portions is the sameas that of the above opening portions 215, 225. In this case, accordingto the size of the electronic part to be accommodated, the total length(the size of the opening) of the outer circumferential line is changed.The aforementioned positional relation is defined as a relation in whichthe outer circumferential line of the opening 225 of the secondstructural member 22 is accommodated inside the outer circumferentialline of the opening 215 of the first structural member 21. However, itis not necessary that the shapes of the outer circumferential lines ofthe communicating holes are the same in the manner shown in thisembodiment, and it is not necessary either that the positional relationsof the opening portions are the same.

The cover sheet 4 covers an upper side of the communicating hole. Thecover sheet 4 is made of prepreg composed of cloth (the thickness: 35μm) impregnated with partially cured epoxy resin.

Each label sheet 51, 52 is formed from a sheet of polyvinyl chloride (85mm×53 mm×25 μm). In this connection, when the thickness of these labelsheets is increased, it is possible to positively protect the electronicparts mounted on the IC card from electrostatic discharge andcontamination. In this case, it is common that the thickness of eachstructural member 21, 22 is adjusted, so that the overall thickness ofthe IC card is made to be a value of the thickness stipulated by ISOStandard.

These label sheets 51, 52 are made to adhere onto the lower surface sideof the circuit board 1 and the upper surface side of the secondstructural member 22. The lower surface side of the circuit board 1 andthe upper surface side of the second structural member 22 are subjectedto sand mat treatment. The reason why sand mat treatment is conducted isdescribed as follows. The surface of a sheet of polyester resin filmcomposing the circuit board 1 or the second structural member 22 is verysmooth. Therefore, appropriate irregularities are formed on the surfaceto be joined with each label sheet so that both surfaces can be moreclosely contacted with each other. However, in the case of the IC cardof this embodiment, curing is conducted while the cover sheet 4 and thesecond structural member 22 are closely contacted with the lower side ofthe label sheet. Therefore, the aforementioned treatment may be omitted.

In the case of the IC card of this embodiment, first, the conductivepattern 14 is formed in a portion on a sheet of film corresponding tothe circuit board 1.

On the other hand, on both sides of the first structural member film,there are provided predetermined quantities of thermoplastic adhesiveagent of ester, so that the adhesive layers 212, 213 can be formed inthe final product, and also on the lower surface of the secondstructural member film, there is provided a predetermined quantity ofthermoplastic adhesive agent of ester, so that the adhesive layer 223can be formed in the final product. After the adhesive layers have beencoated on the surfaces, it is dried. In a portion of the firststructural member film which corresponds to the first structural member21, there is formed an opening 215, and also in a portion of the secondstructural member film which corresponds to the second structural member22, there is formed an opening 225.

In this connection, in this embodiment, in order to enhance theproduction efficiency, a quantity of film to make the circuit boardcorresponding to several pieces of final products was used, however, itis possible to use a quantity of film previously divided into one piece.

Next, the lower surface of the second structural member 22 film was putupon the upper surface of the first structural member 21 film. Further,the lower surface of the first structural member 21 film was put uponthe upper surface of the circuit board 1 film. The above body in whichthe layers were stacked as described above was subjected to hot press(80° C., 40 kgf/cm²) for about 10 minutes and then cooled. In this way,a lamination body was made.

In the communicating holes formed in this lamination body, electronicparts were incorporated by a common method, and wire bonding wasconducted on this lamination body if necessary.

Next, into the above communication holes, a resin encapsulant made offerrite particles and soft epoxy resin was charged. It is preferablethat epoxy resin, the hardness of which is higher than the hardness ofpolyester resin composing the structural member 2, is charged into thecommunication holes instead of the above resin encapsulant, because theelectronic parts can be more strongly protected from a force given tothe IC card from the outside. After curing, this resin encapsulant formsan encapsulant layer 3 to encapsulate the electronic parts located inthe communication holes.

Next, a cover sheet 4 was arranged in a portion surrounding the abovecommunication hole. On the lower surface of the label sheet filmcomposing the label sheet 51, a predetermined quantity of the sameadhesive agent as described before was coated, so that an adhesive agentlayer 513 of 50 μm thickness could be formed in the final product andalso an adhesive agent layer 513 of 85 μm thickness could be formed in aportion where the label sheet was not provided in the final product.After that, the label sheet 51 was arranged on the upper surface of theabove lamination body.

On the upper surface of the label sheet film composing the label sheet52, a predetermined quantity of the same adhesive agent as describedbefore was coated so that an adhesive layer 522 of 85 μm thickness couldbe formed in the final product. After that, the label sheet 52 wasarranged on the lower surface of the above lamination body. Then thelamination body was subjected to hot press (150° C., 40 kgf/cm²) forabout 10 minutes and then cooled.

Next, in a portion of each label sheet film corresponding to each pieceof the final product, predetermined characters and numbers, for example,characters and numbers corresponding to the name of a bank in the caseof the use of a debit card, were printed. In this way, an IC cardarrangement board having 6 pieces of IC cards was manufactured.

This arrangement board was cut into pieces by a common cutting method.In this way, the IC card of this embodiment was made.

In this connection, thus obtained IC card meets the requirements of ISOStandard (85 mm×53 mm×0.76 mm).

In the manufacture of the above IC card, it is not necessary to make asingle body of the IC module which takes time and raises the cost.Further, it is not necessary either to match the outer shape of the ICmodule with the shape of the hole in which the IC module is embedded, sothat a complicated work can be avoided.

Only when the size (the total length of the outer circumference) of eachopening 215, 225 formed in each structural member 21, 22 isappropriately adjusted, it is possible to form a flange-shaped stepportion on the inner wall of the communication hole. Due to the fluidityof an encapsulant charged into this communication hole, thecommunication hole is filled with the encapsulant. Therefore, it ispossible to form an encapsulant layer 3, the outer circumferential shapeof which is the same as the shape of the inner wall of the communicationhole. In this connection, in case blow holes are formed in the stepportion in the communication hole in the process of formation of theencapsulant layer 3, a small through-hole for breathing may be formed inthe periphery of the opening 225 of the second structural member 22.

Due to the arrangement described above in detail, even when the IC cardof the present invention is mistakenly bent while it is carried, theabove step portion tightly holds the encapsulant layer 3, so that theelectronic parts mounted on the IC card can be prevented from comingoff.

Due to the existence of the above step portion, even when the electronicpart mounting device is more intensely bent and the encapsulant layer toencapsulate the electronic parts attempts to separate from the secondopening portion, the separation is stopped at a position close to thesurface of the second opening portion, so that the separation does notreach the first opening portion.

The IC card of the present invention is composed in such a manner thatthe second structural member 22 is arranged on the first structuralmember 21 which is the center of the lamination body, and that thecircuit board 1 is arranged below the first structural member 21, sothat the characteristic of the lamination body such as a thermalexpansion characteristic, and the shape (especially the thickness) ofthe lamination body, are symmetrical in the upward and downwarddirection. Therefore, the entire lamination body is not greatly warped.As a result, the production efficiency can be further enhanced, and theelectronic parts can be more positively prevented from coming off. Sincean inexpensive thin sheet of polyester film of high quality ispositively used for the electronic part mounting device of the presentinvention, the quality of the product can be more positively enhanced,and the cost can be more positively reduced.

Embodiment 2

An IC card of this embodiment is shown in FIG. 4. On the upper side ofthe second structural member 22 having the same opening 225 as that ofEmbodiment 1, there is provided an auxiliary structural member 23 havingthe same auxiliary opening 235 as the opening 215. On the lower side ofthe same circuit board 1 as that of Embodiment 1, there is provided anauxiliary circuit board member 24.

In this case, the thickness of each of the second structural member 22,auxiliary structural member 23, circuit board 1 and auxiliary circuitboard member 24 is determined to be 60 μm. Further, in order to make theoverall thickness of the IC card to meet the requirements of ISOStandard, the thickness of each adhesive layer is changed. Except forthe above points, the IC card of this embodiment is the same as that ofEmbodiment 1. Both the auxiliary structural member 23 and the auxiliarycircuit board member 24 are formed from sheets of film of polyesterresin used for the circuit board 1 in Embodiment 1. Accordingly, thesecond structural member 22 and the circuit board 1 are arranged in asymmetrical relation with respect to the upward and downward direction,and also the auxiliary structural member 23 and the auxiliary circuitboard member 24 are arranged in a symmetrical relation with respect tothe upward and downward direction.

In the IC card of this embodiment, the shape of the second structuralmember 22 is composed in such a manner that it bites into theencapsulant layer 3. Accordingly, compared with the electronic parts inEmbodiment 1, the electronic parts can be more strongly prevented fromcoming off in Embodiment 2.

The longitudinal cross-sectional structure of the IC card of thisembodiment is symmetrical. Accordingly, even when the electronic partsare mounted on the IC card, the occurrence of a great warp can beprevented. The circuit board 1, first structural member 21, secondstructural member 22, auxiliary structural member 23 and auxiliarycircuit board member 24 are formed from considerably thin sheets of film(60 μm). Consequently, although the cost is low, the mechanical strengthis high.

Finally, a variation of the second embodiment by which the same effectcan be provided is exemplarily shown in FIG. 5. In the same manner, avariation of the first embodiment is exemplarily shown in FIG. 6. Likereference characters are used to indicate like parts in FIGS. 1 to 4.

INDUSTRIAL APPLICABILITY

According to the first invention and the second one, even if theelectronic part mounting device is bent, the encapsulant layer toencapsulate the electronic part is engaged with the circuit board or thestructural member arranged inside the outer circumferential line of theencapsulant layer, so that the electronic part can be prevented fromcoming off. Further, the electronic part mounting device of theinvention can be easily manufactured. Therefore, the cost of theelectronic part mounting device can be greatly reduced.

In addition to the effect provided by the second invention describedabove, in the electronic part mounting device of the third invention,even when the electronic part mounting device is more intensely bent andthe encapsulant layer to encapsulate the electronic part is separatedfrom the second opening, the separation appears only in a portion closeto the surface of the second opening, and it does not reach the firstopening. Consequently, it is more difficult for the electronic parts tocome off from the electronic part mounting device.

In addition to the effect provided by the third invention describedabove, in the electronic part mounting device of the fourth invention,when this electronic part mounting device is manufactured, the firststructural member and the second one are stacked on the upper surface ofthe circuit board, and after the electronic part has been mounted on theboard, they are encapsulated by an encapsulant, and a surface member isarranged when necessary. As described above, the manufacturing processis simple. Therefore, it is not necessary at all to manufacture acomplicated IC module which has been conventionally adopted.Consequently, the electronic part mounting device of the presentinvention can be easily and effectively manufactured.

In addition to the effect provided by the fourth invention describedabove, in the electronic part mounting device of the fifth invention,even if the temperatures of the circuit board and the structural membersare changed so that the thermal expansion and shrinkage are caused,since the first structural member is interposed between the circuitboard and the second structural member, they are expanded and shrunk inthe substantially same conditions. Consequently, it is difficult for theelectronic part mounting device of the invention to warp when it ismanufactured and used.

In addition to the effect provided by the fifth invention describedabove, in the electronic part mounting device of the sixth invention, aninexpensive thin sheet of polyester film, the thermal expansion propertyof which is excellent, is positively used. In other words, the cost ofthis electronic part mounting device is very low, and the quality isvery high.

The electronic part mounting device of the seventh invention proposes anIC card to which the effects of the first, second, third, fourth, fifthand sixth invention are remarkably requested.

We claim:
 1. An electronic part mounting device comprising: a lamination body composed of a circuit board and a structural member; an electronic part attached in an opening formed in the lamination body; and an encapsulant layer to encapsulate the electronic part, wherein an outer circumferential line of the opening is arranged inside an outer circumferential line of the encapsulant layer so that the lamination body engages the encapsulant layer.
 2. The electronic part mounting device according to claim 1, CHARACTERIZED in that said opening is composed of said structural member laminated on said circuit board.
 3. The electronic part mounting device according to claim 2, CHARACTERIZED in that said structural member includes: a first structural member having a first opening, arranged on an upper surface side of said circuit board; and a second structural member having a second opening communicated with the first opening, arranged on an upper surface side of the first structural member, and an outer circumferential line of the first opening is arranged outside of an outer circumferential line of the second opening.
 4. The electronic part mounting device according to claim 3, CHARACTERIZED in that said circuit board is made of thermoplastic resin, the length and width of which are substantially the same as those of the final product, said first structural member is mainly made of thermoplastic resin, the length and width of which are substantially the same as those of the circuit board, the first structural member is made to adhere onto an upper surface side of the circuit board with a thermoplastic adhesive agent which is softened at a temperature lower than the softening point of the thermoplastic resin of the circuit board, said second structural member is made to adhere onto an upper surface side of the first structural member with the substantially same adhesive agent as the above thermoplastic adhesive agent, the length and the width of the second structural member are substantially the same as those of the circuit board, and said encapsulant layer is more rigid than the circuit board and the first structural member.
 5. The electronic part mounting device according to claim 4, CHARACTERIZED in that the thickness of said second structural member is substantially the same as the thickness of said circuit board, and the second structural member is made of substantially the same resin as the resin of the circuit board.
 6. The electronic part mounting device according to claim 5, CHARACTERIZED in that said thermoplastic resin is a sheet of polyester film subjected to biaxial orientation and heat-stabilization, and said first structural member is made of the substantially same resin as the resin of said circuit board.
 7. The electronic part mounting device according to claim 1, CHARACTERIZED in that said electronic part mounting device is an IC card. 